Oscillator



Oct. 2, 1962 w. T. HARRIS 3,056,590

OSCILLATOR Filed Feb. 11, 1960 21W Mm ATTORNEYS United fltates Patent 3,9565% OSCILLATOR Wilbur T. Harris, Woodbury, Conn, assignor to The Harris Transducer Corporation, Woodhury, Conn, a corporation of Connecticut Filed Feb. 11, 1960, Ser. No. 8,166 24 Claims. (Cl. 259-1) The present invention relates to a device for producing oscillations, usually in the sonic or ultrasonic range, by causing a fluid to flow through appropriately designed structure.

Devices for producing oscillations of appreciable amplitude and power content in these ranges are required in many applications, for example, in producing ultrasonic vibrations in a fluid within which are suspended devices to be treated (e.g. cleaned, polished or abraded). These oscillations are generally produced by means of essentially electrical or electronic devices, which are often expensive and delicate, and present a substantial maintenance problem when in service.

it is the prime object of the present invention to devise a simple mechanical, rather than electrical or electronic, structure which will effectively produce vibrations of appreciable power content within a predetermined frequency range. It is particularly noteworthy that this is achieved without any moving mechanical parts. An extremely high degree of reliability results.

The device of the present invention utilizes, as the means for providing the power for the oscillations, a flow of fluid, either gas or liquid. When the device is used to produce oscillations for a system in which objects to be treated are immersed in a fluid to which the oscillations are transmitted, the immersing fluid itself can be used to produce the oscillations. In most ultrasonic cleaning systems means are already provided for circulating the immersing fluid, so that use of the oscillator here described for generating the necessary oscillations involves only a very limited expenseboth the fluid and the means for forcing it into the oscillator are already at hand. The reliability and effectiveness of the oscillator of the present invention is such, however, that it may be used to advantage in other systems as well, even where both the fluid and the means for circulating it must be furnished.

The oscillator of the present invention is provided with a pair of resonating chambers the size of which is such, when considered in conjunction with the particular fluid employed, as to permit the fluid to oscillate therein at the frequency of the oscillations desired. These chambers communicate with one another, the communicating means to each chamber joining one another at a junction against which a jet of fluid is directed. The jet of fluid will ideally tend to divide equally between the two chambers, the fluid thereafter escaping from the chambers in any appropriate manner. From a practical point of view, however, there will be random differences at a given instant between the amount of fluid going to one chamber and to the other. An increase in the amount of fluid entering a given chamber will cause the fluid in that chamber to move more rapidly. The resultant aspiration causes the imbalance in the amounts of fluid entering the two chambers to increase until such time as the pressure in the chamber receiving the greater amount of fluid increases to a given value. The jet will then be shifted more toward the other cylinder, pressure will build up in it until the major portion of the jet shifts back to the first cylinder, and so on. The pressure in each cylinder will therefore be seen to vary cyclically, the fluid therein vibrating at a resonant frequency determined by the geometry of the chambers and the characteristics of the particular fluid used. These resonant vibrations may be transmitted from HQQ the chambers to a working station where they can perform useful work.

The transmission of the fluid vibrations may be accomplished in a variety of ways, some of which are here specifically disclosed. The chambers may be provided with vibratable walls which function as diaphragms, the entire housing for the chamber may be so designed as to resonate at the characteristic frequency of the fluid in the chambers, or the pipes or tubes which carry the fluid from the chambers may be resonant at that characteristic frequency.

It is preferred that the chambers be in the form of intersecting cylinders, the fluid entering those cylinders adjacent one axial end and leaving the cylinders adjacent the other axial end. Thus two modes of oscillation are provided in each chamber for the fluid which passes there through, the fluid oscillating circumferentially as it moves around the inside of the cylinder and also oscillating longitudinally of the cylinder. When the oscillations are to be transmitted from the chamber ends it is preferred that the axial length of the cylinder is so chosen as to produce the same resonant frequency for axial fluid vibration within the cylinder as obtains for circumferential fluid vibration.

It will be noted that insofar as the oscillation-producing structure itself is concerned, there are no moving mechanical parts whatsoever. Wear within the device is, for all practical purposes, limited to the junction between the chambers upon which the jet impinges, but the choice of suitable materials for that junction greatly minimizes the wear problem. The simple and sturdy structure facilitates maintenance and replacement of parts if and when wear should occur to an undesirable degree.

To the accomplishment of the above, and to such other objects as may hereinafter appear, the present invention relates to an oscillator structure as defined in the appended claims and as described in this specification, taken together with the accompanying drawings, in. which:

FIG. 1 is a cross sectional view of one embodiment of the present invention taken along the line 11 of FIG. 2;

FIGS. 2 and 3 are cross sectional views taken along the lines 2-2 and 3-3 respectively of FIG. 1; and

FIG. 4 is a front elevational view of an alternative embodiment.

Turning first to the embodiment of FIGS. 1-3, the oscillator comprises a sturdy body 2 of any appropriate material such as steel. A pair of chambers 4 and 6 are formed therein, those chambers being separated by web 8 along their lower portions and communicating with one another, as by intersecting one another, along their upper portions. To this end the body 2 is bored out to define lower bores 4a and 6a respectively which are generally cylindrical in cross section, bores 4b and 6b of larger diameter being formed coaxially thereabove. A pair of hardened steel rings 10 and 12 are secured within the larger bores 41) and 6b respectively, the inner surfaces of the rings 10 and 12 being generally coincident with the inner surfaces of the bores 4a and 6a respectively, those inner surfaces collectively defining the sides of the chambers 4 and 6 respectively. However, as may best be seen from FIG. 2, the inner surfaces of the rings 10 and 12 extend radially outwardly so as to meet one another at junction 14 located substantially midway of the width of the web 8 and to one side of a line through the axes of the chambers 4 and 6. The rings 10 and 12 also narrow to spaced points 16 and 18 respectively above the web 8 and on the other side of the line through the axes of the chambers 4 and 6 from the junction 14, each point 16 and 18 being spaced to opposite sides of a line perpendicular to the line through the chamber axes and passing through the vertex 14, thus defining therebetween a a nozzle opening 20 which is directed toward the junction 14. The rings and 12 may, if desired, be brazed or welded to one another at 22, and the portion thereof defining the junction 14 may be formed of an insert 24 of hard and wear-resistant material such as tungsten carbide.

A vertically extending manifold passage 26 extends downwardly from the top of the body 2 and communicates with the nozzle opening 20', a tube or other conduit 28, through which fluid is pumped to the device, leading to the passage 26.

The upper ends of the chambers 4 and 6 are closed by a top plate 34) secured to the body 2 in any appropriate manner, and a sealing gasket 32 may be interposed between the top plate 30 and the body 2. A pair of fluid escape tubes or conduits 34 and 36 pass through the top cover 30 in sealing relation therewith and extend down into the chambers 4 and 6, those tubes 34 and 36 preferably joining, exteriorly of the body 2, with a common fluid exhaust tube 38. The bottom walls 40 and 42 of the chambers 4 and 6 are, in the embodiment of FIGS. 1-3, rendered vibratable. This may usually be done by making them sufficiently thin to function as diaphragms.

'Fluid is pumped into the tube 28, thereby to be forced through the nozzle opening 20 in the form of a high speed jet. This jet of fluid will impinge upon the junction 14 and divide, some of the fluid entering the chamber 4 and some of the fluid entering the chamber 6. The fluid in each of these chambers will flow circumferentially around the cylindrical interior of those chambers, as indicated by the arrows in FIG. 2, and that fluid will also move downwardly, eventually escaping from the chambers by passing upwardly through the tubes 34 and 36, as indicated by the solid line arrows in FIG. 1.

Under ideal conditions, since the nozzle 20 is symmetrically located relative to the junction 14, the fluid will divide equally between the two chambers 4 and 6. Random vibrations in the amount of fluid entering each chamber will, however, unavoidably occur. If, for example, a greater amount of fluid should enter the chamber 4 than the chamber 6 the fluid in that chamber will be forced to move more rapidly in its circumferential path. A Bernoulli pumping action will result. At first more and more fluid will be sucked or aspirated into the chamber 4, thus further reducing the amount of fluid entering the chamber 6. The pressure in the chamber 4 will increase and the pressure in the chamber 6 will decrease. Ultimately this diiferential in pressure will overcome the aspirating effect, and the jet of fluid emanating from the nozzle 20 will shift over, so that more fluid will now enter chamber 6 than chamber 4. Chamber 6 will suck fluid into itself at the expense of chamber 4 until the pressure in chamber 6 becomes sufficiently greater than the pressure in chamber 4 for the jet to shift again. This shifting of the jet back and forth will continue, the pressures in each of the chambers 4 and 6 alternately increasing and decreasing, the pressure in each chamber 4 or 6 being 180 degrees out of phase with the pressure in the other chamber. Thus oscillations are produced in each chamber.

In the structure shown in FIGS. 1-3 the mean circumferential path of the circulating fluid in each chamber will, when considered in conjunction with the particular fluid being used, determine the frequency at which the oscillations of fluid pressure in each of the chambers will occur. In order to make for most eificient transmission of these oscillations through the diaphragm-like bottom Walls 40 and 42 of the chambers 4 and 6 respectively, those transmitted oscillations being indicated by the broken line arrows in FIG. 1, the axial length of the chambers 4 and 6 is preferably one-half the wave length of the oscillations produced in circumferential movement of the fluid. In this way the fluid in each chamber 4 and 6 will resonate both circumferentially and axially.

When the oscillations are to be transmitted through the t vibratory walls 40 and 42, the body 2 should be acoustically stiff with respect to oscillations of the frequencies involved. If the actuating fluid is a gas, so that the resonant frequencies are in a comparatively low range, a less bulky body 2 need be employed than when the pumped fluid is a liquid.

It is preferred that the nozzle opening 20 and junction 14 be provided over the upper half of the axial length of the chambers 4 and 6, and that the Web 6 be interposed between those chambers, rendering them noncommunicating, over the lower axial half thereof. The fluid exit tubes 34 and 36 extend well into the lower axial halves of the chambers 4 and 6.

A typical embodiment, producing oscillations at a frequency of approximately 20 kc. and utilizing water as the actuating fluid, has chambers 4 and 6 of approximately 1%" inner diameter and 1 /2" axial length, the fluid exit tubes 34 and 36 being formed of diameter copper or stainless steel pipe, the nozzle 26 being provided along the upper /1" of the axial length of the cavities. The width of the nozzle opening 20 is .04". The thickness of the walls 40 and 42 is A If five gallons per minute of water is forced through this device at a pressure drop of pounds per square inch, between 50 and 100 watts of acoustic output will result.

The embodiment of FIG. 4 illustrates different ways in which oscillations may be transmitted from the device. (Similar reference numerals are employed to those used in FIGS. l-3 to indicate similar parts, differentiated, however, by being primed.) As there disclosed the bottom walls 40 and 42 of the chambers 4 and 6' are too thick to function effectively as diaphragms. However, the entire body 2' may be so dimensioned and formed of such material that it is structurally resonant in a lateral direction. Further, it is symmetrical about a line joining the nozzle 20 and junction 14, its length on each side of that line, taking into consideration the characteristics of the material of which it is formed, being one-half the wave length Within itself of oscillations of the frequency produced by the chambers 4' and 6'. With this type of structure the hydraulic oscillatory energy produced within the chambers 4' and 6 will couple to the metal structure of the body 2 itself, which will then radiate the oscillatory energy to the medium surrounding it, as indicated by the arrows 44.

Alternatively, the fluid exit tubes 34 and 36' could be used to deliver the acoustic output of the oscillator to the external medium. Thus those tubes could have a length substantially equal to that of one-half the wave length of the oscillations produced in the chambers 4 and 6, that wave length being computed on the basis of the fluid in which the oscillations are produced. Where the fluid exit tubes 34' and 36 empty directly into the external medium which is to be driven in vibration, as will be the case if they empty into the tank of a supersonic cleaning apparatus, the open mouths of those tubes will effectively deliver the acoustic of the oscillator to the external medium. If, as specifically disclosed in FIG. 4, the fluid exit tubes 34 and 36' join a fluid exhaust tube 38', the connections to the ends of the fluid exit tubes 34' and 36 may be accomplished by means of acoustically transparent rubber hose.

The actuating fluid for the device could take a variety of forms. The device is believed to have its greatest applicability for use in connection with systems where fluid circulation is required for other reasons, since in such systems pumps and conduits for circulating the fluid are already present. For example, in industrial ultrasonic cleaning systems the cleaning fluid is continuously circulated and filtered. That very fluid may, in the course of its circulation, be forced through the chambers 4 and 6, thereby to produce the oscillations which are to be applied to the fluid in the cleaning chamber.

However, the fact that the oscillator of the present invention has no moving mechanical parts inherently makes it so reliable that it may be used to advantage even in systems where fluid circulation means must be provided for the oscillator itself.

Substantially the only place where wear will occur is at the junction 14, upon which the fluid impinges at relatively high velocities. Use of a wear-resistant insert 24 wfll greatly minimize such wear as might occur at this area. If excessive wear should occur, the cover plate 30 can be removed and the rings and 12, or only the insert 24, can be readily replaced. The device can then be reassembled and will be ready for further use with minimal delay and expense.

While but a limited number of embodiments of the present invention are here specifically disclosed, it will be apparent that many variations may be made therein, all within the scope of the instant invention as defined in the following claims.

I claim:

1. An oscillator comprising a housing having a pair of liquid-enclosing resonating chambers with fluid entranceways thereto which meet and communicate at a junction, a nozzle in said housing directed toward said junction substantially symmetrically relative to said fluid entranceways, means for feeding fluid to said nozzle, and means for permitting fluid to escape from said chambers, whereby the fluid in said resonating chambers will oscillate at a predetermined frequency determined by the geometry of said chambers and the nature of said fluid, a part of said housing in operative relation to said resonating chambers being readily vibratable at said predetermined frequency, whereby oscillations of the fluid in said resonating chambers will be communicated to said housing part.

2. An oscillator comprising a housing having a pair of substantially identical liquid-enclosing resonating chambers with fluid entranceways thereto which meet and communicate at an essentially sharp junction, a nozzle in said housing directed toward said junction substantially symmetrically relative to said fluid entranceways, means for feeding fluid to said nozzle, and means for permitting fluid to escape from said chambers, whereby the fluid in said resonating chambers will oscillate at a predetermined frequency determined by the geometry of said chambers and the nature of said fluid, a part of said housing in operative relation to said chambers being readily vibratable at said predetermined frequency, whereby oscillations of the fluid in said resonating chambers will be communicated to said housing part.

3. An oscillator comprising a housing having a pair of substantially cylindrical and substantially parallel similar chambers separated from one another at their lower portions and intersecting one another in an essentially sharpedged junction at their upper portions, a nozzle in said housing directed toward the edge of said junction substantially symmetrically relative to said chambers, end walls closing the ends of said chambers, tubes extending into said chambers at the lower portions thereof, through which tubes fluid can escape from said chambers, and means for feeding fluid to said nozzle, a part of said housing in operative relation to said chambers being vibratable, whereby oscillations set up in said chambers will be communicated to said housing part.

4. An oscillator comprising a housing having a pair of substantially cylindrical and substantially parallel similar chambers separated from one another at their lower portions and intersecting one another in an essentially sharpedged junction at their upper portions, a nozzle in said housing directed toward the edge of said junction substantially symmetrically relative to said chambers, end walls closing the ends of said chambers, tubes passing through the end walls at the upper ends of said chambers and extending into said chambers at the lower portions thereof, through which tubes fluid can escape from said chambers, and means for feeding fluid to said nozzle, a part of said housing in operative relation to said chambers being vibratable, whereby oscillations set up in said chambers will be communicated to said housing part.

5. The oscillator of claim 3, in which said chamber end walls at the lower ends thereof comprise said vibratable part.

6. The oscillator of claim 3, in which said housing is substantially symmetrical about said nozzle and junction and is of such material and dimensions as to resonate at the same frequency as the oscillations produced in said chambers.

7. The oscillator of claim 3, in which said tubes extend beyond said housing and are of such material and dimensions as to resonate at the same frequency as the oscillations produced in said chambers.

8. An oscillator comprising a housing having a pair of chambers with fluid entranceways thereto which meet and communicate at a junction, a nozzle in said housing directed toward said junction substantially symmetrically relative to said fluid entranceways, means for feeding fluid to said nozzle, and means for permitting fluid to escape from said chambers, whereby the fluid in said resonating chambers will oscillate at a predetermined frequency determined by the geometry of said chambers and the nature of said fluid, a part of said housing in operative relation to said chambers being readily vibratable at said predetermined frequency, whereby fluid oscillations set up in said chambers will be communicated to said housing part, said chambers being substantially cylindrical and intersecting one another to define said junction.

9. An oscillator comprising a housing having a pair of chambers with fluid entranceways thereto which meet and communicate at a junction, a nozzle in said housing directed toward said junction substantially symmetrically relative to said fluid entranceways, means for feeding fluid to said nozzle, and means for permitting fluid to escape from said chambers, whereby the fluid in said resonating chambers will oscillate at a predetermined frequency determined by the geometry of said chambers and the nature of said fluid, a part of said housing in operative relation to said chambers being readily vibratable at said predetermined frequency, whereby fluid oscillations set up in said chambers will be communicated to said housing part, said chambers being substantially cylindrical and arranged parallel to one another, said chambers intersecting one another to define said junction.

10. An oscillator comprising a housing having a pair of chambers with fluid entranceways thereto which meet and communicate at a junction, a nozzle in said housing directed toward said junction substantially symmetrically relative to said fluid entranceways, means for feeding fluid to said nozzle, and means for permitting fluid to escape from said chambers, a part of said housing in operative relation to said chambers being vibratable, whereby fluid oscillations set up in said chambers will be communicated to said housing part, said chambers being substantially cylindrical and arranged parallel to one another, said chambers intersecting one another over only a portion of their axial length to define said junction.

11. An oscillator comprising a housing having a pair of chambers with fluid entranceways thereto which meet and communicate at a junction, a nozzle in said housing directed toward said junction substantially symmetrically relative to said fluid entranceways, means for feeding fluid to said nozzle, and means for permitting fluid to escape from said chambers, whereby the fluid in said resonating chambers will oscillate at a predetermined frequency determined by the geometry of said chambers and the nature of said fluid, a part of said housing in operative relation to said chambers being readily vibratable at said predetermined frequency, whereby fluid oscillations set up in said chambers will be communicated to said housing part, said vibratable part comprising end walls of said chambers which are located remote from said fluid en tranceways.

12. An oscillator comprising a housing having a pair of chambers with fluid entranceways thereto which meet and communicate at a junction, a nozzle in said housing directed toward said junction substantially symmetrically relative to said fluid entranceways, means for feeding fluid to said nozzle, and means for permitting fluid to escape from said chambers, whereby the fluid in said resonating chambers will oscillate at a predetermined frequency determined by the geometry of said chambers and the nature of said fluid, a part of said housing in operative relation to said chambers being readily vibratable at said predetermined frequency, whereby fluid oscillations set up in said chambers will be communicated to said housing part, said chambers being substantially cylindrical and defining a circumferential path around which fluid can flow, the mean length of said path corresponding to the wave length of the oscillations to be produced, the axial length of said chambers being approximately onehalf said mean length.

13. An oscillator comprising a housing having a pair of chambers with fluid entranceways thereto which meet and communicate at a junction, a nozzle in said housing directed toward said junction substantially symmetrically relative to said fluid entranceways, means for feeding fluid to said nozzle, and means for permitting fluid to escape from said chambers, whereby the fluid in said resonating chambers will oscillate at a predetermined frequency determined by the geometry of said chambers and the nature of said fluid, a part of said housing in operative relation to said chambers being readily vibratable at said predetermined frequency, whereby fluid oscillations set up in said chambers will be communicated to said housing part, said chambers being substantially cylindrical and defining a circumferential path around which fluid can flow, the mean length of said path corresponding to the wave length of the oscillations to be produced, said vibratable part comprising end walls of said chambers located remote from said fluid entranceways.

14. An oscillator comprising a housing having a pair of chambers with fluid entranceways thereto which meet and communicate at a junction, a nozzle in said housing directed toward said junction substantially symmetrically relative to said fluid entranceways, means for feeding fluid to said nozzle, and means for permitting fluid to escape from said chambers, whereby the fluid in said resonating chambers will oscillate at a predetermined frequency determined by the geometry of said chambers and the nature of said fluid, a part of said housing in operative relation to said chambers being readily vibratable at said predetermined frequency, whereby fluid oscillations set up in said chambers will be communicated to said housing part, said chambers being substantially cylindrical and defining a circumferential path around which fluid can flow, the mean length of said path corresponding to the wave length of the oscillations to be produced, the axial length of said chambers being approximately one-half said mean length, said vibratable part comprising end walls of said chambers located remote from said fluid entranceways.

15. An oscillator comprising a housing having a pair of chambers with fluid entranceways thereto which meet and communicate at a junction, a nozzle in said housing directed toward said junction substantially symmetrically relative to said fluid entranceways, means for feeding fluid to said nozzle, and means for permitting fluid to escape from said chambers, whereby the fluid in said resonating chambers will oscillate at a predetermined frequency determined by the geometery of said chambers and the nature of said fluid, a part of said housing in operative relation to said chambers being readily vibratable at said predetermined frequency, whereby fluid oscillations set up in said chambers will be communicated to said housing part, said housing being substantially symmetrical about said nozzle and junction, one chamber being located to each side of said junction, said housing being of such material and dimensions as to resonate 2% at the same frequency as the oscillations produced in said chambers.

16. An oscillator comprising a housing having a pair of chambers with fluid entranceways thereto which meet and communicate at a junction, a nozzle in said housing directed toward said junction substantially symmetrically relative to said fluid entranceways, means for feeding fluid to said nozzle, and means for permitting fluid to escape from said chambers, whereby the fluid in said resonating chambers will oscillate at a predetermined frequency determined by the geometry of said chambers and the nature of said fluid, a part of said housing in operative relation to said chambers being readily vibratable at said predetermined frequency, whereby fluid oscillations set up in said chambers will be communicated to said housing part, said liquid escape means comprising tubes extending from said housing and of such material and dimensions as to resonate at the same frequency as the oscillations produced in said chambers.

17. An oscillator comprising a housing having a pair of substantially identical chambers with fluid entranceways thereto which meet and communicate at an essentially sharp junction, a nozzle in said housing directed toward said junction substantially symmetrically relative to said fluid entranceways, means for feeding fluid to said nozzle, and means for permitting fluid to escape from said chambers, a part of said housing in operative relation to said chambers being vibratable, whereby oscillations set up in said chambers will be communicated to said housing part, said chambers being substantially cylindrical and arranged parallel to one another, said chambers intersecting one another over only a portion of their axial length to define said junction.

18. An oscillator comprising a housing having a pair of substantially identical chambers with fluid entranceways thereto which meet and communicate at an essentially sharp junction, a nozzle in said housing directed toward said junction substantially symmetrically relative to said fluid entranceways, means for feeding fluid to said nozzle, and menas for permitting fluid to escape from said chambers, whereby the fluid in said resonating chambers will oscillate at a predetermined frequency determined by the geometry or said chambers and the nature of said fluid, a part of said housing in operative relation to said chambers being readily vibratable at said predetermined frequency, whereby oscillations set up in said chambers will be communicated to said housing part, said chambers being substantially cylindrical and defining a circumferential path around which fluid can flow, the mean length of said path corresponding to the wave length of the oscillations to be produced, the axial length of said chambers being approximately one-half said mean length.

19. An oscillator comprising a housing having a pair of substantially identical chambers with fluid entranceways thereto which meet and communicate at an esentially sharp junction, a nozzle in said housing directed toward said junction substantially symmetrically relative to said fluid entranceways, means for feeding fluid to said nozzle, and means for permitting fluid to escape from said chambers, whereby the fluid in said resonating chambers will oscillate at a predetermined frequency determined by the geometry of said chambers and the nature of said fluid, a part of said housing in operative relation to said chambers being readily vibratable, at said predetermined frequency, whereby oscillations set up in said chambers will be communicated to said housing part, said chambers being substantially cylindrical and defining a circumferential path around which fluid can flow, the mean length of said said path corresponding to the wave length of the oscillations to be produced, the axial length of said chambers being approximately one-half said mean length, said vibratable part comprising end walls of said chambers located remote from said fluid entranceways.

20. An oscillator comprising a housing having a pair of substantially identical chambers with fluid entrance- Ways thereto which meet and communicate at an essentially sharp junction, a nozzle in said housing directed to- Ward said junction substantially symmetrically relative to said fluid entranceways, means for feeding fluid to said nozzle, and means for permitting fluid to escape from said chambers, whereby the fluid in said resonating chambers will oscillate at a predetermined frequency determined by the geometry of said chambers and the nature of said fluid, a part of said housing in operative relation 10 2,163,550

to said chambers being readily vibratable at said predetermined frequency, whereby oscillations set up in said 10 chambers will be communicated to said housing part, said housing being substantially symmetrical about said nozzle and junction, one chamber being located] on each side of said junction, said housing being of such material and dimensions as to resonate at the same frequency as the oscillations produced in said chamber.

References Cited in the file of this patent UNITED STATES PATENTS Weaver June 27, 1939 2,262,940 Ish-Shalom Nov. 18, 1941 2,713,998 Eicken July 26, 1955 

